Conventionally, column chromatography has been used for separation and purification of biological substances. However, column separation has some fatal problems as described in the following (1) to (3):    (1) Many kinds of columns have to be used to obtain the target substance, resulting in a poor purification efficiency.    (2) A verification test is required to make sure the target substance is contained in the fractionated ingredients, which means purification is time consuming.    (3) Because of the large purification loss, a large quantity of the sample is required.
On the other hand, for separation and purification of the target substances, affinity particles and affinity columns supporting ligands are used (Patent Document 1 and Patent Document 2).
However, separation and purification using affinity columns have the following problems:    (1) The desired target substance is not selectively separated. That is, in addition to the target substance captured by the ligand, unwanted substances are also adsorbed onto the column.    (2) The capture efficiency is low, which means a large quantity of the liquid sample is required.
The affinity separation method in which affinity particles are dispersed in a liquid sample for separation uses agarose and such (Non-patent Document 1), but this method has the following problems:    (1) The desired target substance is not selectively separated. That is, in addition to the target substance captured by the ligand, unwanted target substances are also adsorbed onto the affinity particles.    (2) The specific gravity is small, which makes the separation of the affinity particles difficult.    (3) The carrier is easily disintegrated, which leads to poor durability.
On the other hand, inorganic particles adsorb more substances than organic particles do, therefore those skilled in the art didn't think of using inorganic particles for affinity particles.
Patent Document 1: Japanese Patent Publication H8-26076
Patent Document 2: Japanese Patent Laid-Open 2002-511141 bulletin
Non-patent Document 1: Bioconjugate Chem.; 2002; 13(2); 163-166